Yes, Spark VDM is part of Spark CDM.
The additional VDM drum machines models and skin were included in the Spark 1.4.1 update.
Spark VDM includes 30 drum machines (analog modeled and sampled), Spark CDM 1.4.1 includes 80 drum machines and kits (using analog modeling, sampling and physical modeling).
Other than the hardware controller, the other important difference is that Spark CDM also allows you to import you own samples (up to 6 velocity layers per instrument) to combine with the Spark instruments.
Spark VDM can only be expanded by Arturia.